Update JGit to 4.9.2.201712150930-r.175-gd8a24ac1c
Update JGit to 4.9.2.201712150930-r.175-gd8a24ac1c

This is a custom build from master, including a merge of all the changes
I recently made to (JGit) stable-4.9. In particular, this change is
necessary so I0092f009 will compile when it is merged from (Gerrit)
stable-2.15 into master.

Change-Id: I3cf28f16cfdc72beea2938987be8130b97765591

GerritCodeReview/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit